Thermally efficient contact-terminal assembly for a switch mechanism



J. P. WATSON l 3,176,108 THERMALLY EFFICIENT CONTACT-TERMINAL March 30,1965 ASSEMBLY FOR A SWITCH MECHANISM Original Filed April 2, 1956 R O mE V m United States Patent Oil ice 3,175,108 Patented Mar. 30, 19653,176,108 THERMALLY EFFICIENT CONTACT-TERMINAL ASSEMBLY FOR A SWITCHMECHANISM James P. Watson, Whittier, Calif.

(59 Waterway Road, Waterway Village, Jupiter, Fla.) Original applicationApr. 2, 1956, Ser. No. 575,467, now

Patent No. 2,964,602, dated Dec. 13, 1960. Divided and this applicationApr. 1, 1960, Ser. No. 24,194

1 Claim. (Cl. 200-166) This invention relates primarily to snap actingmechanisms, and more particularly to a snap acting leaf-springtypeelectric switch, and to an improved terminal for such -a switch and toan improved supporting means for the terminal. However, it will becomeapparent as the description proceeds that the invention is not limitedin its application to snap acting switches, and that the concepts of theinvention are applicable to slow acting switches, relays, circuitbreakers, and the like.

This application is a division of copending application Serial No.575,467 filed April 2, 1956, for Snap Acting Mechanism, whichapplication has now issued as Patent 2,964,602.

It is an object of this invention to provide means for prolonging thecontact life of a switch mechanism, thereby making the mechanism capableof standing many millions of circuit openings and resultant arcformations.

It is another object of this invention to provide improved andsimplified means for installing an electric terminal within a switchhousing.

In accordance with these and other objects which will become apparenthereinafter, preferred forms of the present invention will now bedescribed in connection with the accompanying drawings wherein:

FIG. l is a perspective view partially broken away illustrating a formof switch constructed in accordance with the present invention;

FIG. 2 is a longitudinal section of the switch shown in FIG. 1;

FIG. 3 is a view taken on line 3 3 in FIG. 2, illustrating one half ofthe switch separated at the parting line between the two sections of theswitch housing;

FIG. 4 is a bottom plan view of the switch viewed as indicated by arrow4 in FIG. 2.

In the drawings the present invention is shown as a component of anelectric switch. The switch comprises a leaf spring means in the form ofa rectangular, unbroken leaf or sheet 36 of stiff, springy material suchas beryllium copper. The leaf 36 is pivotally journaled at each end in asupport means shown generally Iat 37. The lower journal axis 38 consistsof a pivot shaft 39 journaled at each end in hubs 41 formed at therespective ends of an openended frame 42. The frame 42 consists of apair of parallel arms 43 which are spanned at their upper ends by anintegrally formed cross piece or arm 44.

The upper journal axis 46 comprises a shaft 47 relieved at 48 to form ajournal portion journaled in a semicircular cavity in -a bearing member49. Opposite the bearing cavity in the member 49 is a transverse pivotpin 51 which is in turn journaled in the cross piece 44 of the frame 42.The lower end of the leaf 36 resides in a longitudinal slot 52 in theshaft 39 and the upper end of the leaf 36 resides in a slot 53 in theshaft 47. The straight line distance between the ends of the leaf 36when thus mounted in the shafts 39 and 47, respectively, is less thanthe actual length of the leaf 36 itself, thereby forcing the leaf toassume a bowed or arched attitude, as shown in FIG. 2.

Near the upper end of the leaf 36, that is the end mounted in the shaft47, the leaf 36 has secured thereagainst an operating means in the formof an electric CIK contact 54, which moves back and forth (FIG. 2) asthe leaf 36 is snapped from one side to the other. A similar contact 56is provided on the opposite side of the leaf 36, las shown in FIG. 2.The contacts 54 and 56 extend laterally across the full width of theleaf 36 as shown in FIG. 3.

In the position shown in FIG. 2, the oper-ating means or contact 54bears forcefully against an operated means, in this instance being anabutment means in the form of a stationary contact 57 iixedly mountedwith respect to the support means 37. The positioning of the contact 57is such that when the leaf is arched to the left as shown in FIG. 2, thecontact 54 bears rmly and forcefully against the stationary contact 57to maintain good electrical contact. A similar stationary contact 58 ispositioned on the opposite side of the leaf 36 and is engaged by theContact 56 when the leaf 36 is snapped to the other side of a linejoining the axis 38 and 46, as shown by the arrowed line 59.

The contact 57 is one of a pair of contacts 5'7 and 61 (FIG. 3) whichare bridged by the movable contact 54 carried by the leaf 36 when theleaf is snapped into the position shown in FIG. 2.V Similarly, thecontact 58 is one of a pair (the other not being shown) which arebridged by the movable contact 56 whenever the leaf 36 is snapped to theright, in FIG. 2. The four contacts thus described are secured to and inelectrical conducting relation with four electrically isolated terminalsthat emerge from the top of the support means 37 and which will bedescribed more in detail hereinafter.

In accordance with the present invention, several means are provided forprolonging switch life by extending contact life. One of the reasons forthe deterioration of contact surfaces in switches is the fact that theheat generated by the arc which is formed whenever the switch is openedis not dissipated rapidly enough, and as a result the localizedtemperature of the switch contact becomes very high. This may be trueeven though other parts of the switch remain relatively cool. Theproblem then is one of immediate and rapid heat dissipation away fromthe local area of the arc. While this may be achieved by the use ofterminals that are relatively large, and bulky, there is a seriousdisadvantage that large terminals projecting from the switch housingresult in relatively small clearances between the terminals withconsequent danger of short circuits as wires must be secured to theterminal. In accordance with the present invention, the terminals 97 towhich the respective contacts 57, 58, 61, etc. are secured, are madewith that portion of the terminal which is inside the housing andimmediately adjacent the contacts relatively large At the same time,only a relatively small or narrow elongate portion 98 projects throughthe wall of the housing 62 to become the external terminal to which thewires are connected. The mass of the terminal 97 within the housing isseveral times that of the mass 98 which is outside of the housing andthe terminal is made of a material having a high specific heat, such ascopper. The terminals thus constitute a relatively large heat sump forthe temporary storage of high temperature heat generated by arcing atthe relatively thin contacts 57 etc., which are preferably made of aprecious metal having high heat conductivity such as silver. Since thearcing time is a relatively minor fraction of the total switching cycle,the heat generated by the arc at the contacts 57 etc., rapidlydissipates into the much larger mass of the terminal 97 withoutappreciably raising the temperature of the terminal 97. From the heatsump constituted by the terminal 97 the heat is continuously conductedthrough the external portion 98- to the ambient atmosphere.

The casing or housing 62, which is preferably formed of non-conductingmaterial, is made in two sections, with the parting line normal to theshaft means 71 as shown at sturdvmeansiare `provided'for securingthe-terminal 97 Y As shown'in FIGS. 1, 2, and 3,

within the housing 62.

the external portions98 of the terminals 97 pass through correspondingrectangular'openings 103 formed in the top ywall of the housing 62. Theinner end of each terminal 97 is provided with YaV laterally projectingtoe orV boss 104 adapted to engage in a notch l106 formed in the ysidewall 107 of the housing 62, to create a notch and'boss engagementfbetweenthe terminal and the housing.:V The terminalA 1971s* pressedinto the rectangular passage 163 from the inside,'until the toe11M-snaps intoposition in the notch 106. In this Way, the terminals areheld rmly and securely .in position'without requiring 'any bondingsubstance. i

Y Whilethe instant invention has been shown and def scribed `herein inwhat is conceived to be the mostpractical andpreferred embodiment, itvis recognized that departures may be made therefrom within the scope ofthe invention, which is therefore not to be limited to the detailsdisclosed herein, but is tobeaiorded the full scope of the claim.V

What is claimed is: In a switch mechanismV enclosedy :within acasing theprovisionof improved stationary contactsutilizing one pieceterminal-heat sink means comprising:

electrically isolated -terminals Voutwardly projecting in parallelarrangement from a common external'surface of said casingand'so arrangedas to provide Y maximum clearance from one 1another;feach said specificheat value, such as copper; said stationary y contact being formed of acorrosion resistant met-al possessing `high heat conductivity, such assilver; the securement embracingthe, entire mating area between saidstationary contact yand Sadi enlarged portion.

`References Cited by` theEXaminel--V UNITED STATES PATENTS 1,149,0548/15 Hoppeet al 200-166v 1,173,562 2/16 DitChani v 20G-166 1,691,20311/28 Lee et al.V y 1,913,522 6/33 Thompson etal.y 20G-166 2,217,48810/40 Mahnke. 2,439,402 4/43 Stilwell '....mw 20G-166 2,448,509 9/48 fAntIly et a1. 339-117 2,647,225 7/53 Cole er a1: 2,909,756 k1.0/59 Sitz339-217 X 2,921,240 1/60 Cole 200-166 X FGREIGN PATENTS 130,557 8/ 19Great Britain.

787,777 7/35 France.' Y

VBERNirRD A. YGiLHEANY,Primary Examiner. Mm(` L. LEVY, Examiaeaj

